1. Field of the Invention
The present invention generally relates to deposition of a metal layer onto a substrate. More particularly, the present invention relates to a modular cell to be used within an electro-chemical deposition or electroplating system.
2. Background of the Related Art
Electroplating has been previously limited in integrated circuit design to the fabrication of lines on circuit boards. Electroplating is now used to deposit metals (such as copper) such as on a seed layer contained within features (e.g., vias, trenches, or contacts) and over the fields surrounding these features. One feature filling embodiment that utilizes electroplating requires initially depositing a diffusion barrier layer on the substrate. A seed layer is deposited (typically by physical vapor deposition) to form a plating surface on the substrate. Metal is then deposited by electroplating on the seed layer on the substrate. The seed layer is typically formed from the same metal as the subsequently electroplated metal, so the deposited seed layer becomes contiguous with the deposited metal. Finally, the deposited metal can be planarized by another process, e.g., chemical mechanical polishing (CMP), to define the conductive interconnect feature.
Electroplating is performed by establishing a voltage/current level between the seed layer on the substrate and a separate anode (both the seed layer and the substrate are contained within the conductive electrolyte solution) to deposit metal ions on the layer to form the deposited metal. The resulting positive metal ions (for example Cu+) are attracted to, and deposited on, the negatively charged substrate surface.
Electroplating is performed in electrolyte cells that normally have an opening, and which are filled with electrolyte solution. Electrolyte cells comprise an anode, a controller, and an associated substrate holder. The substrate holder secures a substrate in a position so the substrate can be inserted through the opening, and the substrate seed layer is immersed in the electrolyte solution. The anode is also positioned in the electrolyte solution within the electrolyte cell. An electric current/voltage is established through the electrolyte solution between the anode and the seed layer on the substrate. The electrolyte solution contains the metal ions that are deposited on the substrate seed layer to form the metal film during the electroplating process.
The electrolyte cells need to be maintained and/or repaired occasionally. For example, the anode chemically reacts with the electrolyte solution when immersed therein, and the chemical reaction disperses metal ions, such as copper sulfate (that can be electrically dissociated into distinct copper and sulfate ions). The chemical reaction between the anode and the electrolyte solution also degrades the anode and causes the anode to be irregularly-shaped. The shape of the anode also can affect the shape of the electromagnetic field generated between the anode and the seed layer. An irregularly shaped electric field results in uneven deposition of metal across the surface of the seed layer during the electroplating process. When the anodes become overly worn, they must be replaced to maintain uniformity of deposition across the substrate seed layer.
The electrolyte cell is removed from the electroplating system during maintenance and/or repair. To remove an electrolyte cell from the electroplating system, the electrolyte solution is removed from the electrolyte cell and the electrolyte cell is removed from its mount. Accordingly, the electroplating system is unusable during repair of the cell, thereby resulting in loss of production and increased cost of operation of the electroplating system.
Therefore, there remains a need for an electroplating or other electro-chemical deposition system in which the down-time of the entire electroplating system for maintenance and repair of the electrolyte cell is minimized.
The present invention generally provides a method and apparatus for depositing metal on a substrate. One embodiment of method for removing a modular metal deposition cell from a deposition cell mount comprises:unfastening a fastener that secures a cell top to a cell bottom, and also fastens the cell top and the cell bottom to the deposition cell mount. The cell top or the cell bottom are removed from the deposition cell mount.